The purpose of this project is to explore the causes and prevention of tardive dyskinesia. We will explore our epidemiological studies of factors related to the presence or absence of dyskinesia. We will follow a cohort of 120 patients with early dyskinesia for two years to obtain currently non-existent information on the course of such dyskinesias. Patients able to be taken off antipsychotic drugs who then relapse will be randomly assigned to thioridazine or their "best" prior antipsychotic and followed. Video tapes will be taken to help accurately quantify changes in dyskinesia over time. In 80 patients with more persistent dyskinesia, lithium will be compared to placebo both in terms of its early (2 month) effects on dyskinetic movements and its ability to allow patients to remain stable while having their antipsychotic medication tapered for 6 months then withdrawn for one year. Patients relapsing on placebo will have a comparable trial on lithium. We will attempt to characterize chronic "schizophrenic" patients who respond well to lithium. Studies of other drugs proposed as treatments for tardive dyskinesia will also be run (lecithin, clonazepam, and clozapine-like drugs). We will attempt to approximate the annual incidence of new dyskinesia at McLean Hospital, a 250-bed private psychiatric hospital.